TAIPEI » A senior Chinese envoy arrived in Taiwan on Monday to sign an agreement on sharing medical information and cooperating in the development of new drugs, amid rapidly improving ties between the once bitter foes.

Chen Yunlin, head of the quasi-governmental Chinese organization responsible for implementing relations with Taiwan, is expected to remain on the island for about 48 hours.

His visit constitutes one of two high-level meetings held between the sides every year. They were begun as part of Taiwanese President Ma Ying-jeou’s historic effort to strengthen links with Beijing and reduce cross-strait tensions, which have now eased to their lowest level since the island split from the mainland amid civil war in 1949.

Somewhat against the grain, a planned investment protection agreement will not be signed during this round of negotiations — the sixth since Ma became president in May 2008 — because China rejects a Taiwanese demand that international arbitrators adjudicate investment-related disputes.

Taiwanese officials have said the new medical agreement will facilitate cross-strait exchanges of information on epidemics in each other’s territories and cooperation in the development of vaccines to counter any outbreak.

The deal also will allow the two sides to work together on the clinical trial of new drugs, a step that Taiwanese officials say will accelerate the entry of Taiwanese products into the lucrative mainland market.

Since Ma took office 2 1/2 years ago, he has shepherded the signing of more than a dozen China-related commercial agreements, including a wide-ranging tariff reduction deal signed in June that his government says will help revitalize the sluggish Taiwanese economy.

A small number of anti-China activists are planning protests this time, but Taiwan’s main opposition Democratic Progressive Party is not endorsing their action — in contrast to the strong backing it gave for mass rallies to protest Chen’s arrival two years ago — a reflection of just how routine these meetings have become.

However, the DPP continues to insist that Ma’s push to link Taiwan’s high-tech economy ever closer to mainland markets is bad for the island’s future, because it undermines the competitiveness of its once strong light industrial sector, and opens the door to increasing Chinese influence. The party says that influence will erode the island’s democratic character and threaten its de facto independence.